POS Debugging

Debugging tips:

• PHP notices, warnings, and errors are logged to log/php-errors.log.
• Failed SQL queries are logged to log/queries.log
• Optionally, state change logging may be enabled on the Debug tab. It writes to log/core_debug.log. This quickly generates a ludicrous quantity of information but can be useful to figure out what a state value isn't the expected value.
• The "test" subdirectory has an input parsing tester. If a command seems to do nothing, this shows the raw output. The result should always be valid JSON.